2 * Copyright (c) 2000 Damien Miller. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. All advertising materials mentioning features or use of this software
13 * must display the following acknowledgement:
14 * This product includes software developed by Markus Friedl.
15 * 4. The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35 #include <openssl/rand.h>
36 #include <openssl/sha.h>
41 # define offsetof(type, member) ((size_t) &((type *)0)->member)
44 /* Print lots of detail */
45 /* #define DEBUG_ENTROPY */
47 /* Number of times to pass through command list gathering entropy */
48 #define NUM_ENTROPY_RUNS 1
50 /* Scale entropy estimates back by this amount on subsequent runs */
51 #define SCALE_PER_RUN 10.0
53 /* Minimum number of commands to be considered valid */
54 #define MIN_ENTROPY_SOURCES 16
56 #define WHITESPACE " \t\n"
59 # define RUSAGE_SELF 0
61 #ifndef RUSAGE_CHILDREN
62 # define RUSAGE_CHILDREN 0
65 #if defined(EGD_SOCKET) || defined(RANDOM_POOL)
68 /* Collect entropy from EGD */
69 void get_random_bytes(unsigned char *buf, int len)
71 static int egd_socket = -1;
73 char egd_message[2] = { 0x02, 0x00 };
74 struct sockaddr_un addr;
77 memset(&addr, '\0', sizeof(addr));
78 addr.sun_family = AF_UNIX;
80 /* FIXME: compile time check? */
81 if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
82 fatal("Random pool path is too long");
84 strlcpy(addr.sun_path, EGD_SOCKET, sizeof(addr.sun_path));
86 addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);
88 if (egd_socket == -1) {
89 egd_socket = socket(AF_UNIX, SOCK_STREAM, 0);
91 fatal("Couldn't create AF_UNIX socket: %s", strerror(errno));
92 if (connect(egd_socket, (struct sockaddr*)&addr, addr_len) == -1)
93 fatal("Couldn't connect to EGD socket \"%s\": %s", addr.sun_path, strerror(errno));
97 fatal("Too many bytes to read from EGD");
99 /* Send blocking read request to EGD */
100 egd_message[1] = len;
102 c = atomicio(write, egd_socket, egd_message, sizeof(egd_message));
104 fatal("Couldn't write to EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));
106 c = atomicio(read, egd_socket, buf, len);
108 fatal("Couldn't read from EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));
110 #else /* !EGD_SOCKET */
112 /* Collect entropy from /dev/urandom or pipe */
113 void get_random_bytes(unsigned char *buf, int len)
115 static int random_pool = -1;
118 if (random_pool == -1) {
119 random_pool = open(RANDOM_POOL, O_RDONLY);
120 if (random_pool == -1)
121 fatal("Couldn't open random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
124 c = atomicio(read, random_pool, buf, len);
126 fatal("Couldn't read from random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
128 #endif /* RANDOM_POOL */
129 #endif /* EGD_SOCKET */
132 * Seed OpenSSL's random number pool from Kernel random number generator
140 debug("Seeding random number generator");
141 get_random_bytes(buf, sizeof(buf));
142 RAND_add(buf, sizeof(buf), sizeof(buf));
143 memset(buf, '\0', sizeof(buf));
146 #else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
149 * FIXME: proper entropy estimations. All current values are guesses
150 * FIXME: (ATL) do estimates at compile time?
151 * FIXME: More entropy sources
154 /* slow command timeouts (all in milliseconds) */
155 /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
156 static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
158 static int prng_seed_loaded = 0;
159 static int prng_seed_saved = 0;
160 static int prng_commands_loaded = 0;
164 /* Proportion of data that is entropy */
166 /* Counter goes positive if this command times out */
167 unsigned int badness;
168 /* Increases by factor of two each timeout */
169 unsigned int sticky_badness;
170 /* Path to executable */
172 /* argv to pass to executable */
174 /* full command string (debug) */
178 double stir_from_system(void);
179 double stir_from_programs(void);
180 double stir_gettimeofday(double entropy_estimate);
181 double stir_clock(double entropy_estimate);
182 double stir_rusage(int who, double entropy_estimate);
183 double hash_output_from_command(entropy_source_t *src, char *hash);
185 /* this is initialised from a file, by prng_read_commands() */
186 entropy_source_t *entropy_sources = NULL;
189 stir_from_system(void)
191 double total_entropy_estimate;
194 total_entropy_estimate = 0;
197 RAND_add(&i, sizeof(i), 0.5);
198 total_entropy_estimate += 0.1;
201 RAND_add(&i, sizeof(i), 0.5);
202 total_entropy_estimate += 0.1;
205 RAND_add(&i, sizeof(i), 0.0);
207 RAND_add(&i, sizeof(i), 0.0);
209 total_entropy_estimate += stir_gettimeofday(1.0);
210 total_entropy_estimate += stir_clock(0.5);
211 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
213 return(total_entropy_estimate);
217 stir_from_programs(void)
221 double entropy_estimate;
222 double total_entropy_estimate;
223 char hash[SHA_DIGEST_LENGTH];
225 total_entropy_estimate = 0;
226 for(i = 0; i < NUM_ENTROPY_RUNS; i++) {
228 while (entropy_sources[c].path != NULL) {
230 if (!entropy_sources[c].badness) {
231 /* Hash output from command */
232 entropy_estimate = hash_output_from_command(&entropy_sources[c], hash);
234 /* Scale back entropy estimate according to command's rate */
235 entropy_estimate *= entropy_sources[c].rate;
237 /* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
238 if (entropy_estimate > SHA_DIGEST_LENGTH)
239 entropy_estimate = SHA_DIGEST_LENGTH;
241 /* Scale back estimates for subsequent passes through list */
242 entropy_estimate /= SCALE_PER_RUN * (i + 1.0);
245 RAND_add(hash, sizeof(hash), entropy_estimate);
248 debug("Got %0.2f bytes of entropy from '%s'", entropy_estimate,
249 entropy_sources[c].cmdstring);
252 total_entropy_estimate += entropy_estimate;
254 /* Execution times should be a little unpredictable */
255 total_entropy_estimate += stir_gettimeofday(0.05);
256 total_entropy_estimate += stir_clock(0.05);
257 total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
258 total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
261 debug("Command '%s' disabled (badness %d)",
262 entropy_sources[c].cmdstring, entropy_sources[c].badness);
265 if (entropy_sources[c].badness > 0)
266 entropy_sources[c].badness--;
273 return(total_entropy_estimate);
277 stir_gettimeofday(double entropy_estimate)
281 if (gettimeofday(&tv, NULL) == -1)
282 fatal("Couldn't gettimeofday: %s", strerror(errno));
284 RAND_add(&tv, sizeof(tv), entropy_estimate);
286 return(entropy_estimate);
290 stir_clock(double entropy_estimate)
296 RAND_add(&c, sizeof(c), entropy_estimate);
298 return(entropy_estimate);
299 #else /* _HAVE_CLOCK */
301 #endif /* _HAVE_CLOCK */
305 stir_rusage(int who, double entropy_estimate)
307 #ifdef HAVE_GETRUSAGE
310 if (getrusage(who, &ru) == -1)
313 RAND_add(&ru, sizeof(ru), entropy_estimate);
315 return(entropy_estimate);
316 #else /* _HAVE_GETRUSAGE */
318 #endif /* _HAVE_GETRUSAGE */
324 _get_timeval_msec_difference(struct timeval *t1, struct timeval *t2) {
325 int secdiff, usecdiff;
327 secdiff = t2->tv_sec - t1->tv_sec;
328 usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec);
329 return (int)(usecdiff / 1000);
333 hash_output_from_command(entropy_source_t *src, char *hash)
335 static int devnull = -1;
338 int cmd_eof = 0, error_abort = 0;
339 struct timeval tv_start, tv_current;
340 int msec_elapsed = 0;
345 int total_bytes_read;
349 devnull = open("/dev/null", O_RDWR);
351 fatal("Couldn't open /dev/null: %s", strerror(errno));
355 fatal("Couldn't open pipe: %s", strerror(errno));
357 (void)gettimeofday(&tv_start, NULL); /* record start time */
359 switch (pid = fork()) {
363 fatal("Couldn't fork: %s", strerror(errno));
366 dup2(devnull, STDIN_FILENO);
367 dup2(p[1], STDOUT_FILENO);
368 dup2(p[1], STDERR_FILENO);
373 execv(src->path, (char**)(src->args));
374 debug("(child) Couldn't exec '%s': %s", src->cmdstring,
376 src->badness = src->sticky_badness = 128;
378 default: /* Parent */
382 RAND_add(&pid, sizeof(&pid), 0.0);
386 /* Hash output from child */
388 total_bytes_read = 0;
390 while (!error_abort && !cmd_eof) {
395 (void) gettimeofday(&tv_current, 0);
396 msec_elapsed = _get_timeval_msec_difference(&tv_start, &tv_current);
397 if (msec_elapsed >= entropy_timeout_current) {
401 msec_remaining = entropy_timeout_current - msec_elapsed;
404 FD_SET(p[0], &rdset);
405 tv.tv_sec = msec_remaining / 1000;
406 tv.tv_usec = (msec_remaining % 1000) * 1000;
408 ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
418 bytes_read = read(p[0], buf, sizeof(buf));
419 if (bytes_read == -1) {
424 SHA1_Update(&sha, buf, bytes_read);
425 total_bytes_read += bytes_read;
426 RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
434 debug("Command '%s': select() failed: %s", src->cmdstring,
440 RAND_add(&tv, sizeof(&tv), 0.0);
441 } /* while !error_abort && !cmd_eof */
443 SHA1_Final(hash, &sha);
448 debug("Time elapsed: %d msec", msec_elapsed);
451 if (waitpid(pid, &status, 0) == -1) {
452 debug("Couldn't wait for child '%s' completion: %s", src->cmdstring,
457 RAND_add(&status, sizeof(&status), 0.0);
460 /* closing p[0] on timeout causes the entropy command to
461 * SIGPIPE. Take whatever output we got, and mark this command
463 debug("Command '%s' timed out", src->cmdstring);
464 src->sticky_badness *= 2;
465 src->badness = src->sticky_badness;
466 return(total_bytes_read);
469 if (WIFEXITED(status)) {
470 if (WEXITSTATUS(status)==0) {
471 return(total_bytes_read);
473 debug("Command '%s' exit status was %d", src->cmdstring,
474 WEXITSTATUS(status));
475 src->badness = src->sticky_badness = 128;
478 } else if (WIFSIGNALED(status)) {
479 debug("Command '%s' returned on uncaught signal %d !", src->cmdstring,
481 src->badness = src->sticky_badness = 128;
488 * prng seedfile functions
491 prng_check_seedfile(char *filename) {
495 /* FIXME raceable: eg replace seed between this stat and subsequent open */
496 /* Not such a problem because we don't trust the seed file anyway */
497 if (lstat(filename, &st) == -1) {
498 /* Fail on hard errors */
500 fatal("Couldn't stat random seed file \"%s\": %s", filename,
507 if (!S_ISREG(st.st_mode))
508 fatal("PRNG seedfile %.100s is not a regular file", filename);
510 /* mode 0600, owned by root or the current user? */
511 if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid()))
512 fatal("PRNG seedfile %.100s must be mode 0600, owned by uid %d",
519 prng_write_seedfile(void) {
525 /* Don't bother if we have already saved a seed */
531 pw = getpwuid(getuid());
533 fatal("Couldn't get password entry for current user (%i): %s",
534 getuid(), strerror(errno));
536 /* Try to ensure that the parent directory is there */
537 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
539 mkdir(filename, 0700);
541 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
544 debug("writing PRNG seed to file %.100s", filename);
546 RAND_bytes(seed, sizeof(seed));
548 /* Don't care if the seed doesn't exist */
549 prng_check_seedfile(filename);
551 if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1)
552 fatal("couldn't access PRNG seedfile %.100s (%.100s)", filename,
555 if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
556 fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
563 prng_read_seedfile(void) {
569 pw = getpwuid(getuid());
571 fatal("Couldn't get password entry for current user (%i): %s",
572 getuid(), strerror(errno));
574 snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
577 debug("loading PRNG seed from file %.100s", filename);
579 if (!prng_check_seedfile(filename)) {
580 verbose("Random seed file not found, creating new");
581 prng_write_seedfile();
583 /* Reseed immediatly */
584 (void)stir_from_system();
585 (void)stir_from_programs();
589 /* open the file and read in the seed */
590 fd = open(filename, O_RDONLY);
592 fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
595 if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
596 verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
598 memset(seed, '\0', sizeof(seed));
602 /* stir in the seed, with estimated entropy zero */
603 RAND_add(&seed, sizeof(seed), 0.0);
608 * entropy command initialisation functions
611 prng_read_commands(char *cmdfilename)
622 entropy_source_t *entcmd;
624 f = fopen(cmdfilename, "r");
626 fatal("couldn't read entropy commands file %.100s: %.100s",
627 cmdfilename, strerror(errno));
630 entcmd = (entropy_source_t *)xmalloc(num_cmds * sizeof(entropy_source_t));
631 memset(entcmd, '\0', num_cmds * sizeof(entropy_source_t));
635 while (fgets(line, sizeof(line), f)) {
641 /* skip leading whitespace, test for blank line or comment */
642 cp = line + strspn(line, WHITESPACE);
643 if ((*cp == 0) || (*cp == '#'))
644 continue; /* done with this line */
646 /* First non-whitespace char should be double quote delimiting */
649 error("bad entropy command, %.100s line %d", cmdfilename,
654 /* first token, command args (incl. argv[0]) in double quotes */
655 cp = strtok(cp, "\"");
657 error("missing or bad command string, %.100s line %d -- ignored",
658 cmdfilename, linenum);
661 strlcpy(cmd, cp, sizeof(cmd));
663 /* second token, full command path */
664 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
665 error("missing command path, %.100s line %d -- ignored",
666 cmdfilename, linenum);
670 /* did configure mark this as dead? */
671 if (strncmp("undef", cp, 5) == 0)
674 strlcpy(path, cp, sizeof(path));
676 /* third token, entropy rate estimate for this command */
677 if ((cp = strtok(NULL, WHITESPACE)) == NULL) {
678 error("missing entropy estimate, %.100s line %d -- ignored",
679 cmdfilename, linenum);
682 est = strtod(cp, &argv);
685 if ((cp = strtok(NULL, WHITESPACE)) != NULL) {
686 error("garbage at end of line %d in %.100s -- ignored", linenum,
691 /* save the command for debug messages */
692 entcmd[cur_cmd].cmdstring = xstrdup(cmd);
694 /* split the command args */
695 cp = strtok(cmd, WHITESPACE);
699 char *s = (char*)xmalloc(strlen(cp) + 1);
700 strncpy(s, cp, strlen(cp) + 1);
701 entcmd[cur_cmd].args[arg] = s;
703 } while ((arg < 5) && (cp = strtok(NULL, WHITESPACE)));
705 if (strtok(NULL, WHITESPACE))
706 error("ignored extra command elements (max 5), %.100s line %d",
707 cmdfilename, linenum);
709 /* Copy the command path and rate estimate */
710 entcmd[cur_cmd].path = xstrdup(path);
711 entcmd[cur_cmd].rate = est;
713 /* Initialise other values */
714 entcmd[cur_cmd].sticky_badness = 1;
718 /* If we've filled the array, reallocate it twice the size */
719 /* Do this now because even if this we're on the last command,
720 we need another slot to mark the last entry */
721 if (cur_cmd == num_cmds) {
723 entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_source_t));
727 /* zero the last entry */
728 memset(&entcmd[cur_cmd], '\0', sizeof(entropy_source_t));
731 entropy_sources = xrealloc(entcmd, (cur_cmd+1) * sizeof(entropy_source_t));
733 debug("loaded %d entropy commands from %.100s", cur_cmd, cmdfilename);
735 return (cur_cmd >= MIN_ENTROPY_SOURCES);
739 * Write a keyfile at exit
742 prng_seed_cleanup(void *junk)
744 prng_write_seedfile();
748 * Conditionally Seed OpenSSL's random number pool from
749 * syscalls and program output
754 void *old_sigchld_handler;
756 if (!prng_commands_loaded) {
757 if (!prng_read_commands(SSH_PRNG_COMMAND_FILE))
758 fatal("PRNG initialisation failed -- exiting.");
759 prng_commands_loaded = 1;
762 /* Make sure some other sigchld handler doesn't reap our entropy */
764 old_sigchld_handler = signal(SIGCHLD, SIG_DFL);
766 debug("Seeding random number generator.");
767 debug("OpenSSL random status is now %i\n", RAND_status());
768 debug("%i bytes from system calls", (int)stir_from_system());
769 debug("%i bytes from programs", (int)stir_from_programs());
770 debug("OpenSSL random status is now %i\n", RAND_status());
772 signal(SIGCHLD, old_sigchld_handler);
775 fatal("Couldn't initialise builtin random number generator -- exiting.");
777 if (!prng_seed_loaded)
779 prng_seed_loaded = 1;
781 prng_read_seedfile();
782 fatal_add_cleanup(prng_seed_cleanup, NULL);
783 atexit(prng_write_seedfile);
786 #endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */